sync_settings_ui 0.5.0: BackupSlot.json on data_transfer

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01WzxdWXTUM9dpnCS2wtFkx4

sync_settings_ui/.gitignore

@@ -4,3 +4,4 @@ build/
 pubspec.lock
 coverage/
 *.iml
+pubspec_overrides.yaml

sync_settings_ui/lib/src/backup_slot.dart

@@ -1,12 +1,15 @@
+import 'package:data_transfer_flutter/data_transfer_flutter.dart';
+
 /// An injectable local export/import delegate for [SyncSettingsScreen]'s
 /// optional "Backup" section.
 ///
-/// Deliberately not a shared implementation: the actual export/import format
-/// differs per app (todo: Markdown notes; home_inventory: inventory export;
-/// workout_app: a permission-gated `BackupService`), so this package only
-/// carries the label and the two callbacks. Passing `null` for
-/// `SyncSettingsScreen.backup` omits the section entirely (diet_guard,
-/// wake_alarm have no local backup at all).
+/// The export/import CONTENT differs per app (todo: Markdown notes;
+/// home_inventory: inventory export; workout_app: a permission-gated
+/// `BackupService`), so the default constructor only carries the label and
+/// the two callbacks. Apps whose backup is a JSON file use [BackupSlot.json],
+/// which adds the shared file plumbing (`data_transfer_flutter`). Passing
+/// `null` for `SyncSettingsScreen.backup` omits the section entirely
+/// (diet_guard, wake_alarm have no local backup at all).
 class BackupSlot {
   /// Creates a [BackupSlot] labelled [label] (e.g. `'notes'`,
   /// `'inventory'`), backed by [export] and [import].
@@ -16,6 +19,28 @@ class BackupSlot {
     required this.import,
   });
 
+  /// A slot whose backup is a JSON file, using `data_transfer_flutter`.
+  ///
+  /// Export saves `build()` as [fileName] to device storage (system Save-as
+  /// on Android/iOS, a save dialog on desktop, a download on web). Import
+  /// lets the user pick a JSON file and hands the decoded object to
+  /// [restore]; a cancelled picker restores nothing.
+  factory BackupSlot.json({
+    required String label,
+    required String fileName,
+    required Future<Map<String, Object?>> Function() build,
+    required Future<void> Function(Map<String, Object?> json) restore,
+  }) => BackupSlot(
+    label: label,
+    export: () async {
+      await exportJson(fileName: fileName, json: await build());
+    },
+    import: () async {
+      final json = await pickJson();
+      if (json != null) await restore(json);
+    },
+  );
+
   /// Noun describing what this exports/imports, used in the section's
   /// button text ("Export $label" / "Import $label").
   final String label;

sync_settings_ui/pubspec.yaml

@@ -5,7 +5,7 @@ description: >-
   injected closures -- no keystore or platform plugin access lives in this
   package itself.
 publish_to: 'none'
-version: 0.4.3
+version: 0.5.0
 
 environment:
   sdk: ^3.12.2
@@ -16,6 +16,11 @@ dependencies:
       url: https://github.com/kuhyx/utils
       ref: crdt_sync_dart-v0.11.3
       path: crdt_sync_dart
+  data_transfer_flutter:
+    git:
+      url: https://github.com/kuhyx/utils
+      ref: data_transfer_flutter-v0.1.0
+      path: data_transfer_flutter
   flutter:
     sdk: flutter
 

sync_settings_ui/test/backup_slot_test.dart

@@ -1,3 +1,6 @@
+import 'dart:convert';
+
+import 'package:data_transfer_flutter/data_transfer_flutter.dart';
 import 'package:flutter_test/flutter_test.dart';
 import 'package:sync_settings_ui/sync_settings_ui.dart';
 
@@ -16,4 +19,83 @@ void main() {
     expect(exported, isTrue);
     expect(imported, isTrue);
   });
+
+  group('BackupSlot.json', () {
+    late _FakePlatform fake;
+    late DataTransferPlatform original;
+
+    setUp(() {
+      original = DataTransfer.platform;
+      fake = _FakePlatform();
+      DataTransfer.platform = fake;
+    });
+
+    tearDown(() => DataTransfer.platform = original);
+
+    test('export saves the built map under fileName', () async {
+      final slot = BackupSlot.json(
+        label: 'inventory',
+        fileName: 'inv.json',
+        build: () async => {'items': 3},
+        restore: (_) async {},
+      );
+
+      await slot.export();
+
+      expect(fake.saved.single.$1, 'inv.json');
+      expect(jsonDecode(fake.saved.single.$2), {'items': 3});
+    });
+
+    test('import hands the picked map to restore', () async {
+      fake.picked = '{"items":3}';
+      Map<String, Object?>? restored;
+      final slot = BackupSlot.json(
+        label: 'inventory',
+        fileName: 'inv.json',
+        build: () async => {},
+        restore: (json) async => restored = json,
+      );
+
+      await slot.import();
+
+      expect(restored, {'items': 3});
+    });
+
+    test('a cancelled picker restores nothing', () async {
+      var called = false;
+      final slot = BackupSlot.json(
+        label: 'inventory',
+        fileName: 'inv.json',
+        build: () async => {},
+        restore: (_) async => called = true,
+      );
+
+      await slot.import();
+
+      expect(called, isFalse);
+    });
+  });
+}
+
+class _FakePlatform implements DataTransferPlatform {
+  String? picked;
+  final saved = <(String, String)>[];
+
+  @override
+  Future<bool> saveText({
+    required String fileName,
+    required String text,
+  }) async {
+    saved.add((fileName, text));
+    return true;
+  }
+
+  @override
+  Future<bool> shareText({
+    required String fileName,
+    required String text,
+  }) async => true;
+
+  @override
+  Future<String?> pickText() async => picked;
 }